Investigation of rock drill bits

The object of this thesis is an attempt to determine the relative efficiency of rock drill bits. The bits compared were the ordinary double chisel bit, sharpened with a Leyner drill sharpener, and the same bit after it had been filed so that the point was not sharp, but a flat surface 3/32 of an inch wide at the outside, diameter of the bit and tapering to a point at the center of the bit --page 1